Heretofore, most metals and other substances have been held in the molten state or melted through the use of fossil fuels. These fossil fuels and their resultant extracted energy are introduced into the material to be made or held molten either through immersion tube heating or through radiation by reverberation from refractory chambers.
Due to the recent energy crisis, industry has vociferously expressed a dire need for heating or holding materials in a molten condition through the use of electrical energy. In general, electric heating of liquids or molten metals is not in and of itself new. Heretofore, furnaces have been designed which electrically heat liquids or molten metals by radiation from above the surface of these liquids, or by sheathed immersion elements within these liquids. One of the primary limiting factors to such previous electric heating of these liquids have been the limiting energy input, either through the surface by electric radiation, or within the liquid by immersion heaters. For example, zinc adversely attacks or dissolves immersion tubes which are heated either with fossil fuels or electric resistance heating elements if they are constructed of ferrous alloys. On the other hand, ceramic immersion tubes are too fragile and are generally limited to inputs of 15-50 kilowatts per immersion tube of approximately 10-12 inches in diameter by three feet or more in length of immersion.
Various industries have expressed an urgent need for electric immersion heating element systems which will offer reasonable service life and yet be capable of introducing energies in the order of 100 kilowatts to 200 kilowatts per square foot of immersion tube area.
The present invention fulfills the urgent need expressed by industry, and also avoids the limitations and drawbacks of the prior art equipment and techniques.